Customizing WordPress RSS Feed is very easy if you know how HTML works, but most WordPress Users do not know how to change codes especially in modifying the default RSS feed Widget. Majority of Blog Owners who are using this default available widget are syndicating Contents from the other source URL to there Sidebar in the form of News Flash or Updates from the Original Site. The main problem regarding the default WordPress widget, when you click the feed, you are redirected to the feed URL instead of having an option to open the link to a new window and having the option to vary the link into a "no follow" attribute.
To Fix these Problem without knowing how to program. Check the Better RSS Widget Plug-in.
Download their Developers Plugin at this Page http://wordpress.org/extend/plugins/better-rss-widget/ .
Unlike the Default RSS Feed Sidebar, the Better WordPress RSS Sidebar Plug-in has the functionality of adding "no follow" to outbound links and the ability to open target links to a new window that gives you the benefit of total control over your links, but not only that, you may choose where to display the Feed and Cache Setting is not a Problem.
There are plug ins that are more flexible than this one but I still prefer the simplicity of this tool.
There's a simple way to customize WordPress RSS Sidebar Display using the "Better RSS Feed Widget" Free WordPress plug-in. I hope this simple article solves your problem.